It is well known that yarn using machines, such as said knitting machines, yarn is not directly supplied from a spool, cop, reel or the like, but such yarn arrives from the spool to the yarn machine after having been previously wound up on an apparatus, where a reserve or supply of yarn is built up and then delivered to the yan using machine with constant and controlled tension or with constant lengths of yarn per time unit.
The known apparatus is substantially in the form of a drum, to one end of which turns or windings of yarn are wound, the yarn being drawn off from the other end of the drum. Rigid and swinging mechanical members are then provided which act on the windings of yarn wound on the drum, causing translation thereof from that end of the drum, to which they are fed, to the other end where the yarn is drawn off. In some apparatus, such as those disclosed in published German Patent Application No. 2,301,416, U.S. Pat. No. 3,796,386, French Patent No. 1,285,954 or corresponding German Patent No. 1,191,197, the yarn being drawn off passes through a hole in the central portion of the drum on which the yarn windings are wound.
For the translation of the yarn windings along the outer surface of the drum, mechanical members of different nature are known. In accordance with the above cited patents, as well as U.S. Pat. Nos. 3,419,225 and 2,625,340 and still other patents, adjacent that end of the drum where yarn winding is carried out, provision is made for a disc or plate swinging relative to the drum, this disc or plate having an arc of its surface always contacting a section of that winding of said windings which is closest thereto. Plate oscillation takes place about an axis which is inclined with respect to the drum axis, so that the contact zone between said plate and the yarn winding adjacent thereto continuously changes throughout the drum periphery. Thus, said plate urges or pushes the winding off, leaving a free space, in which another winding is continuously distributed. That winding which is pushed off by the plate, in turn pushes the winding adjacent thereto, the latter pushing off the next winding, and so on, causing a simultaneous displacement of the whole winding package wound up on the drum.
This winding translation system suffers from serious disadvantages residing, for example, in that with particular yarns the windings tend to overlap, the windings tend to bind against one another if the yarn is of a pile character, and should the yarn break at any location, the windings would loosen and overlap, making it difficult to find out the free end of the broken yarn.
Also other systems are known for yarn displacement on the drum, such as that disclosed in U.S. Pat. No. 1,052,212, wherein the apparatus comprises two sets of circumferential bars and members for radially and axially moving each set of bars relative to the other set, so that each set of bars alternatively takes up the yarn wound up about said sets of bars, axially displaces it and allows it to move on the other set of bars. Also this displacement or translation system for yarn windings has substantial shortcomings residing, for example, in that the windings have a tendency to freely drop or fall down and overlap (which is avoided by importing a high tension to the yarn incoming on the apparatus), no control for the position of the yarn windings is available, and still that, should a yarn break, windings would tend to fall down and it would be difficult to find out the free end of the broken yarn.
In some apparatus of the prior art, in which the drum rotates about its own axis, an additional shortcoming then arises in that the yarn, at limited sections of its length, may undergo objectionable twist changes at steps wherein the using machine does not draw off any yarn, while the involved apparatus continues to rotate.
In many apparatus of the prior art, the yarn being drawn off therefrom, would freely run off, that is without any brake, so that, particularly should the yarn be drawn off intermittently and at high speed, upon sudden discontinuity of this drawing off, the yarn may all the same run off the drum by inertia and accordingly overlap or build up knots. In order that this be avoided, it has been proposed that the peripheral surface of the drum should be acted on by an element for braking and controlling the tension of the outgoing yarn, the element comprising a ring having flexible fingers projecting therefrom and bearing on the drum. These fingers are deflected by the yarn being drawn off, controlling the tension thereof. Such a type of braking device is disclosed, for example, in U.S. Pat. No. 2,838,922.
The braking devices of this character suffer from disadvantages residing, for example, in being suitable to provide a fixed constant tension, and in that at the start of rotation of the drum about its own axis, the device applied thereto tends to slip and accordingly to run off and to overlap the yarn windings adjacent thereto.
The prior art apparatus suffers then from a further shortcoming, in that when the yarn is run off at high speed from the drum forming part of each apparatus, the yarn running off from the drum forms a balloon due to the centrifugal force, that is the yarn tends to be moved away from the drum to a large extent, thus making impossible any control on the speed and tension of the outgoing yarn.